In the field of medical diagnostic imaging, two or more items of image data in plural time phases are acquired and angiostenosis is assessed or a tissue lesion is detected based on a difference between the images.
The image data acquired in plural time phases can be used to detect an abnormal area through inter-image comparison or a fusion process. Also, a subtraction process between the image data acquired in plural time phases will allow a reference image (subtraction image) for assessment of angiostenosis to be generated from the image data acquired in plural time phases.
In order to improve accuracy of the inter-image comparison and subtraction image, it is important to improve accuracy of registration between images resulting from the image data of plural time phases. Thus, various techniques have been developed for registration between images resulting from image data of plural time phases.
However, between the images resulting from image data of plural time phases, there are often variations in pixel values due to movements of a subject or a contrast medium. Therefore, it is very difficult to perform registration between images with high accuracy.
Also, in the subtraction process, due to changes in image characteristics caused by contrast imaging, some rigid portions do not lend themselves to registration. In this case, displacement of a rigid portion left unaligned will result in misregistration, causing an artifact in the subtraction image and adversely affecting diagnosis.